Researchers at Dartmouth University have found that a 3D printed shape covered in aluminum foil can improve wireless range and increase Wi-Fi security. The project, which appeared on Eurekalert, involves placing a reflector on and around a Wi-Fi router’s antennae to shape the beam, increasing range and preventing it from passing through to unwanted spaces.

“With a simple investment of about $35 and specifying coverage requirements, a wireless reflector can be custom-built to outperform antennae that cost thousands of dollars,” said Xia Zhou, a Dartmouth assistant professor.

In their paper, Zhou and his colleagues tested multiple styles of directional antennas and also tested an “anecdotal” solution that involved sticking a soda can behind a router to shape the radio waves towards a target. After a few iterations, they were able to create specific shapes to increase Wi-Fi reception in specific rooms. They then created a program called WiPrint that 3D prints the exact shape needed to form the beams for better coverage and security. Once printed all you have to do is cover them in aluminum foil.

The team found that their reflectors could accurately shape Wi-Fi beams to avoid some spaces and favor others, thereby increasing security and coverage. For example, you could shape your beam to avoid going out a window into the street but be stronger in a room nearby.

They haven’t yet released the software but rest assured that your grandpa was right: aluminum foil and antennas do mix.